I have never seen and assume there Is not a gasket made for the flanged connection on the gas tank fill tube for a 36 1/2 ton . I have not had any luck with gasket maker material, even those that resist gasoline, they all seen to still allow a leak at the joint. Has anyone found a gasket or a good gasket material that works?
Thanks, Richard
Richard,
I'll take a look at mine a little later today. I had it apart when I took my tank in for repairs a couple of years ago, but I've forgotten what was in that joint (which does not leak!). I don't believe I had to replace it after the tank repair.
Wally
Wally, thanks I appreciate It. I see you are the featured Chat Guy, Speech!
Richard
"My fellow Chevrolians..."
You guys might be interested in an upcoming issue of the G&D which will be devoted only to TRUCKS!!!
Don't tell anyone that I told you. 
Have you tried neopreme rubber? JIM
I have not, since I couldn't find a source for a thick material to cut a gasket. Any thoughts where I might find this?
Thanks,
Richard
Try NAPA; if they do not have it, they may know where to get you need...JIM
Richard,
OK, here's the setup on my truck. An O-ring (about 2-1/2" ID, 1/8" width) sits on a ridge in the flared end of the lower section, and mates with the tapered ID of the "gas cap" section. I assume the O-ring is neoprene to resist gas. I'm going to replace mine as it has a shredded side from my previous installation (probably dry). This time I'll use some grease to lube it as it is tightened. I'm also installing a new, tight neoprene washer under the hex bolt that holds the assembly together.
Wally
Wally, thanks for taking It apart to look. I know It Is a pain to get to. I guess I will be out o ring shopping.
Richard
McMaster-Carr is a good source for things you cant find elsewere. They would have the neoprene in many thickness.
For an example, I got brake rivets from them that I could not find elsewere.
Thanks, I will check them.
Richard
If you find the o-ring, use spray silicone lube on the rubber and it slides right in. NAPA has a good supply of o-rings too...JIM
Will do, thanks for the tips.
Richard